November 8, 1997

Letters

Correct me if I'm wrong . . .

Perhaps long-time couples recall better than randomly paired folks because after all those years, they'll actively correct each other -- something they might not do with strangers ("Partners in Recall," SN: 9/13/97, p. 174). How about testing other long-time groups, like sisters, bowling buddies, and friends?

C.A. Richards
Merrick, N.Y.

You're right. Elderly couples in Roger Dixon's studies often correct each other and generally have a good sense for when to accept a correction that turns out to be accurate. -- B. Bower

Mixing motivations?

The contention that mother rats' "style of caring" for their offspring "may tailor their [the pups'] stress reactions" may result from the researchers' anthropomorphizing their data ("Well-groomed rodents stay cool, calm," SN: 9/13/97, p. 167). The specifics of the experiment, as reported, are that handled pups are groomed more by their mothers than nonhandled pups and that the more handled and groomed pups exhibit less evidence of stress as adults. The mothers groom pups to remove chemical scents acquired from human handlers and the human environs. This undesirable odor, from a mother rat's point of view, motivates her behavior.

William Hamer
Marion, Ill.

Why sands stay put

I just read "Dry Sand, Wet Sand" (SN: 9/20/97, p. 186) and want to comment that adhesion between two flat, glassy surfaces is greatly enhanced with a little bit of water. Glass slides and slide covers are a great example of that. Thus, any surfaces in maximal contact might tend to stay that way, while other contacts shift until they maximize as well.

Also, most of the weight in a sand pile is not located directly under the middle of the pile. Couldn't that be due to the fact that the weight of each sand grain is transmitted through the contact point between it and an adjacent grain? Since you have 180° out of the possible 360° (if you consider only two dimensions), the chances of lateral contacts are much greater than those of contact directly below. Thus, on average, the weight-bearing load will be transmitted to one side or the other.

Anne Barton Wittke
Flagstaff, Ariz.

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